东秦岭淅川奥陶、志留纪地层的新观察  

NEW OBSERVATION ON THE ORDOVICIAN AND SILURIAN ROCKS IN XICHUAN(EAST QINLING),WESTERN HENAN,CENTRAL CHINA

作　　者：戎嘉余[1] 詹仁斌[1] 王怿[1] 黄冰[1] 唐鹏[1] 栾小聪 

机构地区：[1]现代古生物学和地层学国家重点实验室,中国科学院南京地质古生物研究所,江苏南京210008

出　　处：《地层学杂志》2015年第1期1-14,共14页Journal of Stratigraphy

基　　金：国家基金委创新研究群体项目(41221001);重大研究项目(41290260);现代古生物学和地层学国家重点实验室的大力支持;IGCP 591项目的阶段成果

摘　　要：2014年对豫西淅川县境奥陶纪、志留纪地层考察后取得如下认识:1)上奥陶统碎屑岩相地层(如上集王罐沟)宜统称为蛮子营组,灰岩、泥岩相(如大石桥石燕河)从下到上宜称为杨庄村组、石燕河组和刘家坡组;2)根据腕足类,石燕河组(含Rongatrypa动物群)和张湾组下部(含Cathaysiorthis动物群)分别归于晚奥陶世凯迪中晚期和志留纪兰多维列世鲁丹早中期,推测本区缺失凯迪阶顶部、赫南特阶和鲁丹阶底部地层;3)Cathaysiorthis动物群的发现说明本区发育比Pristiograptus leei带更低的地层;4)若岞■组属于早奥陶世的结论可信,则本区缺失中奥陶统,约有10 Myr未接受海相沉积;5)晚奥陶世华北型和北美中大陆型的牙形类与中、东亚腕足动物群和志留纪初期典型华南型腕足动物群的发育表明,当时北美、中东亚的许多块体位于热带海域,由于北美与我国许多块体相距甚远,腕足动物交流受限明显,但牙形类可沿着赤道环流交流。4.5亿年前后,本区在地层序列、地质发展史、沉积环境、生物相和生物组合特性上,情况较复杂,上奥陶统的似更近似于华北,而志留系的与华南关系更密切,并很可能一直持续到泥盆纪晚期。Preliminary investigation on the Upper Ordovician and lower Silurian Llandovery in Xichuan, western Henan reveal new observations. 1） The clastic Upper Ordovician in the research area should be called the Manziying Formation as a whole （e. g. at Wangguangou of Shangji town）, while those localities with both limestones and mudstones include the Yangzhuangcun, Shiyanhe and the Liujiapo formations in ascending order （e. g. at Shiyanhe of Dashiqiao town）. 2） According to the conodonts conodont and brachiopods biostratigraphic data, the Shiyanhe Formation （with the Rongatrypa brachiopod fauna） and the lower Zhangwan Formation （with the Cathaysiorthis brachiopod fauna） may be of respectively, the middle Katian （Late Ordovician） and early-middle Rhuddanian （Llandovery, Silurian） age and the top Katian the Hirnantian and the basal Rhuddanian （lasted for about 2 Myr） are probably missing in the area studied. 3） The Ordovician-Silurian boundary is placed between the Manziying and the Zhangwan formations, i.e. at a disconformity between these two formations. The discovery of the Cathaysiorthis fauna indicates that the rocks older than the Pristiograptus leei biozone were deposited in the research area. 4） The Zuoqu Formation may be of Early Ordovician age, and hence the entire Middle Ordovician is missing there, i.e. without deposition for about 10 Myr in this part of the South China paleoplate. 5） During the Late Ordovician, the conodont fauna of North China and Mid-Continental （North American） type and the central to eastern Asian brachiopod fauna developed, but transitioned to typical shelly fauna of South China type at the beginning of Silurian. Such paleobiogeographic transition shows that South China, North China, North America, and central-eastern Asia might have been all around the paleoequator during the Ordovician-Silurian transition, and biotic exchanges were facilitated by equatorial ocean currents.

关 键 词：腕足动物群 生物地层 上奥陶统 兰多维列统 志留系 淅川 东秦岭 河南 

分 类 号：P534.42[天文地球—古生物学与地层学] P534.43[天文地球—地质学]